|Publication number||US7531461 B2|
|Application number||US 11/225,891|
|Publication date||May 12, 2009|
|Filing date||Sep 14, 2005|
|Priority date||Sep 14, 2005|
|Also published as||CN100557776C, CN101263582A, US20070056926, WO2007040752A2, WO2007040752A3|
|Publication number||11225891, 225891, US 7531461 B2, US 7531461B2, US-B2-7531461, US7531461 B2, US7531461B2|
|Original Assignee||Tokyo Electron Limited|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (15), Non-Patent Citations (12), Referenced by (2), Classifications (8), Legal Events (5)|
|External Links: USPTO, USPTO Assignment, Espacenet|
This application is related to co-pending U.S. application Ser. No. 11/225,893, entitled “Process and System For Etching Doped Silicon”, filed on even date herewith. The entire contents of this application is herein incorporated by reference in its entirety.
The present invention relates to a method and system for etching a doped silicon layer on a substrate using a dry plasma process, and more particularly to a method and system for etching a doped silicon layer using a process gas comprising SF6 and a fluorocarbon gas.
As is known to those in the semiconductor art, the reduction in size of semiconductor devices has been indispensably necessary in order to cause an increase in device performance and a decrease in power consumption. For instance, in keeping with the pace of modern technology, integrated circuits (ICs), including, for example, field-effect transistors (FETs), are now formed with gate lengths less than 50 nm. However, as gate lengths are formed below 50 nm, FET scaling becomes limited by the configuration of these devices, including the methods by which they are fabricated. For example, as VLSI technology approaches the limits in scaling, there currently exist several device structures under consideration, namely, a bulk MOSFET (metal-oxide-semiconductor FET), a dual-gate MOSFET, and a SOI (silicon-on-insulator) MOSFET. During the fabrication of advanced semiconductor devices, silicon layers are etched while critical dimensions of the feature formed therein are maintained. Often times, this requires the etching of a shallow doped silicon region, followed by the etching of an un-doped silicon region, each of which having an optimal process chemistry to facilitate preservation of the feature critical dimension.
The present invention relates to a method and system for etching a doped silicon layer on a substrate. The method comprises using a process composition having SF6 and a fluorocarbon gas.
Additionally, the present invention relates to a method and system for etching a silicon layer, wherein the silicon layer comprises a doped silicon sub-layer that extends through a portion of the thickness of the silicon layer. The method comprises etching the doped silicon sub-layer using a first process composition, and optionally etching the remaining un-doped silicon layer using a second process composition. The first process composition comprises SF6 and a fluorocarbon gas.
According to an embodiment, a method of etching a silicon layer on a substrate is described, wherein the substrate having the silicon layer including a dopant is disposed in a plasma processing system. A process composition comprising SF6 and a fluorocarbon gas is introduced to the plasma processing system. A plasma is formed from the process composition in the plasma processing system. The substrate is exposed to the plasma in order to etch the silicon layer. Furthermore, according to another embodiment, a computer readable medium is employed which includes a program for performing the method.
According to yet another embodiment, a plasma processing system for etching a silicon layer on a substrate is described, including a plasma processing chamber for facilitating the formation of a plasma from a process composition in order to etch the silicon layer, wherein the silicon layer comprises a dopant. A controller, coupled to said plasma processing chamber, is configured to execute a process recipe utilizing the process composition. The process composition comprises SF6 and a fluorocarbon gas.
In the accompanying drawings:
In material processing methodologies, pattern etching comprises the application of a thin layer of light-sensitive material, such as photoresist, to an upper surface of a substrate that is subsequently patterned in order to provide a mask for transferring this pattern to the underlying thin film during etching. The patterning of the light-sensitive material generally involves exposure by a radiation source through a reticle (and associated optics) of the light-sensitive material using, for example, a micro-lithography system, followed by the removal of the irradiated regions of the light-sensitive material (as in the case of positive photoresist), or non-irradiated regions (as in the case of negative resist) using a developing solvent.
For example, as shown in
The silicon layer 4 comprises doped silicon sub-layer 7 that extends through a portion of the thickness of the silicon layer 4. In the etching process for transferring the pattern 2 into silicon layer 4, the doped silicon sub-layer 7 s etched using a first process composition. The dopant concentration in the silicon sub-layer can range from substantially no dopant to the maximum concentration attainable for the dopant in silicon. For example, the dopant may be phosphorus and the dopant concentration may range from approximately no phosphorus dopant to the maximum concentration of approximately 5E+21 atoms per cubic centimeter, or alternatively, the concentration may range from approximately 1E+20 atoms per cubic centimeter to approximately 4E+20 atoms per cubic centimeter. The first process composition may be utilized to etch the remaining un-doped silicon sub-layer 8. Optionally, the remaining un-doped silicon sub-layer 8 is etched using a second process composition.
Underlying the silicon layer 4, an etch stop layer (not shown) may be employed to facilitate the end of the etching process while preventing the etching process from penetrating the underlying layers of substrate 5. For example, the etch stop layer can include silicon nitride or silicon carbide for silicon processing. Additionally, a dielectric layer (not shown) may underlie the silicon layer 4. For instance, the dielectric layer can include an oxide layer, such as a silicon dioxide (SiO2) layer, a high dielectric constant (high-k) dielectric layer, an oxynitride layer, such as a silicon oxynitride layer, etc. Once the etching process is performed, remnants of the light-sensitive material and post-etch residue 8 are left on surfaces of feature 9. For example, remnants of the light-sensitive material and post-etch residue may be found on the flat field (or upper surface of the substrate), the sidewalls of feature 9, or the bottom of feature 9.
To transfer pattern 2 into silicon layer 4 according to an embodiment, the doped silicon sub-layer 7 is etched by introducing a first process composition comprising SF6 and a fluorocarbon gas, and thereafter forming plasma. The fluorocarbon gas may be represented as CxFy, where x and y are integers greater than or equal to unity. For example, the fluorocarbon gas can include any one or a combination of two or more of C4F8, C5F8, C3F6, C4F6, etc. Alternatively, the fluorocarbon gas may be represented as CHxFy, where x and y are integers greater than or equal to unity. For example, the fluorocarbon gas can include CHF3 and/or CH2F2, or the like. Additionally, the first process composition can include an inert gas, such as a noble gas (e.g., He, Ne, Ar, Kr, Xe). The remaining un-doped silicon sub-layer 8 can be etched by introducing a second process composition comprising a halogen containing compound. For example, the halogen containing compound can include HBr, Cl2, or SF6 or any combination thereof. Additionally, the second process composition can include an inert gas, such as a noble gas (e.g., He, Ne, Ar, Kr, Xe). Additionally, the process composition can include an oxygen containing compound, such as O2, CO, or CO2, or any combination of two or more thereof or the like. Although the process recipe is presented as a two step process, it may include a single step utilizing the first process composition to etch both the doped silicon sub-layer 7 and the un-doped silicon sub-layer 8.
According to one embodiment, a plasma processing system 1 is depicted in
According to the embodiment depicted in
Substrate 25 can be affixed to the substrate holder 20 via an electrostatic clamping system. Furthermore, substrate holder 20 can further include a cooling system including a re-circulating coolant flow that receives heat from substrate holder 20 and transfers heat to a heat exchanger system (not shown), or when heating, transfers heat from the heat exchanger system. Moreover, gas can be delivered to the back-side of substrate 25 via a backside gas system to improve the gas-gap thermal conductance between substrate 25 and substrate holder 20. Such a system can be utilized when temperature control of the substrate is required at elevated or reduced temperatures. For example, the backside gas system can comprise a two-zone gas distribution system, wherein the helium gas gap pressure can be independently varied between the center and the edge of substrate 25. In other embodiments, heating/cooling elements, such as resistive heating elements, or thermo-electric heaters/coolers can be included in the substrate holder 20, as well as the chamber wall of the plasma processing chamber 10 and any other component within the plasma processing system 1 a.
In the embodiment shown in
Alternately, RF power is applied to the substrate holder electrode at multiple frequencies. Furthermore, impedance match network 50 serves to improve the transfer of RF power to plasma in plasma processing chamber 10 by reducing the reflected power. Match network topologies (e.g. L-type, □-type, T-type, etc.) and automatic control methods are well known to those skilled in the art.
Vacuum pump system 30 can, for example, include a turbo-molecular vacuum pump (TMP) capable of a pumping speed of 5000 liters per second (and greater) and a gate valve for throttling the chamber pressure. In conventional plasma processing devices utilized for dry plasma etch, a 1000 to 3000 liter per second TMP is generally employed. TMPs are useful for low pressure processing, typically less than about 50 mTorr. For high pressure processing (i.e., greater than about 100 mTorr), a mechanical booster pump and dry roughing pump can be used. Furthermore, a device for monitoring chamber pressure (not shown) can be coupled to the plasma processing chamber 10. The pressure measuring device can be, for example, a Type 628B Baratron absolute capacitance manometer commercially available from MKS Instruments, Inc. (Andover, Mass.)
Controller 14 comprises a microprocessor, memory, and a digital I/O port capable of generating control voltages sufficient to communicate with and activate inputs to plasma processing system 1 a as well as monitor outputs from plasma processing system 1 a. Moreover, controller 14 can be coupled to and can exchange information with RF generator 40, impedance match network 50, the gas injection system (not shown), vacuum pump system 30, as well as the backside gas delivery system (not shown), the substrate/substrate holder temperature measurement system (not shown), and/or the electrostatic clamping system (not shown). For example, a program stored in the memory can be utilized to activate the inputs to the aforementioned components of plasma processing system 1 a according to a process recipe in order to perform the method of etching a doped silicon layer. One example of controller 14 is a DELL PRECISION WORKSTATION 610™, available from Dell Corporation, Austin, Tex.
Controller 14 may be locally located relative to the plasma processing system 1 a, or it may be remotely located relative to the plasma processing system la via an internet or intranet. Thus, controller 14 can exchange data with the plasma processing system 1 a using either a direct connection, an intranet, or the internet, or any combination thereof. Controller 14 may be coupled to an intranet at a customer site (i.e., a device maker, etc.), or coupled to an intranet at a vendor site (i.e., an equipment manufacturer). Furthermore, another computer (i.e., controller, server, etc.) can access controller 14 to exchange data via either a direct connection, an intranet, or the internet, or any combination thereof.
The diagnostic system 12 can include an optical diagnostic subsystem (not shown). The optical diagnostic subsystem can comprise a detector such as a (silicon) photodiode or a photomultiplier tube (PMT) for measuring the light intensity emitted from the plasma. The diagnostic system 12 can further include an optical filter such as a narrow-band interference filter. In an alternate embodiment, the diagnostic system 12 can include a line CCD (charge coupled device), a CID (charge injection device) array, or a light dispersing device such as a grating or a prism, or any combination thereof. Additionally, diagnostic system 12 can include a monochromator (e.g., grating/detector system) for measuring light at a given wavelength, or a spectrometer (e.g., with a rotating grating) for measuring the light spectrum such as, for example, the device described in U.S. Pat. No. 5,888,337.
The diagnostic system 12 can include a high resolution Optical Emission Spectroscopy (OES) sensor such as from Peak Sensor Systems, or Verity Instruments, Inc. Such an OES sensor has a broad spectrum that spans the ultraviolet (UV), visible (VIS), and near infrared (NIR) light spectrums. The resolution is approximately 1.4 Angstroms, that is, the sensor is capable of collecting 5550 wavelengths from 240 to 1000 nm. For example, the OES sensor can be equipped with high sensitivity miniature fiber optic UV-VIS-NIR spectrometers which are, in turn, integrated with 2048 pixel linear CCD arrays.
The spectrometers receive light transmitted through single or bundled optical fibers, where the light output from the optical fibers is dispersed across the line CCD array using a fixed grating. With the configuration described above, light transmitted through an optical vacuum window can be focused onto the input end of the optical fibers via a convex spherical lens. Three spectrometers, each specifically tuned for a given spectral range (UV, VIS and NIR), form a sensor for the process chamber 10. Each spectrometer includes an independent A/D converter. And lastly, depending upon the sensor utilization, a full emission spectrum can be recorded every 0.1 to 1.0 seconds.
Alternatively, the diagnostic system 12 can include a Model SE3000 spectroscopic ellipsometer, commercially available from SOPRA.
In the embodiment shown in
In the embodiment shown in
In the embodiment shown in
Alternately, the plasma can be formed using electron cyclotron resonance (ECR). In yet another embodiment, the plasma is formed from the launching of a Helicon wave. In yet another embodiment, the plasma is formed from a propagating surface wave. Each plasma source described above is well known to those skilled in the art.
In the following discussion, a method of etching a silicon layer having a doped silicon sub-layer utilizing a plasma processing device is presented. The plasma processing device can comprise various elements, such as described with respect to
In one embodiment, a method of etching a doped silicon layer, such as a phosphorus doped layer, employs a process composition comprising SF6 and a fluorocarbon gas, such as CH2F2, CHF3, or C4F8, or the like. For example, a process parameter space can comprise a chamber pressure of about 5 to about 1000 mTorr, an SF6 process gas flow rate ranging from about 10 to about 500 sccm, a C4F8 process gas flow rate ranging from about 10 to about 500 sccm, an upper electrode (e.g., element 70 in
In one example, a method of etching a doped silicon sub-layer utilizing a plasma processing device such as the one described in
Etch rate (nm/min)
In another example, a method of etching a doped silicon sub-layer utilizing a plasma processing device such as the one described in
The first exemplary process recipe includes: Chamber pressure=about 10 mTorr; Upper electrode RF power=about 100 W; Lower electrode RF power=about 200 W; Process gas flow rate SF6/C4F8=about 60/40 sccm; an electrode spacing of about 140 mm between the lower surface of electrode 70 (see
60 nm STRUCTURE
80 nm STRUCTURE
As shown in Table 2, the offset in trim amount between isolated structures and nested structures is reduced when using the SF6/C4F8 chemistry. With either chemistry, the offset can be approximately 10% of the DCD or less.
In 420, a plasma is formed in the plasma processing system from the first process composition using, for example, any of the systems described in
In 430, the substrate comprising the doped silicon layer is exposed to the plasma formed in 420 in order to etch through the doped silicon layer.
Optionally, in 440, a second process composition is introduced to the plasma processing system, wherein the second process composition comprises a halogen containing gas. Alternately, the second process composition can further comprise an inert gas, such as a noble gas.
Optionally, in 450, a plasma is formed in the plasma processing system from the second process composition using, for example, any of the systems described in
Optionally, in 460, the substrate is exposed to the plasma formed in 450 in order to etch through the remaining undoped silicon layer.
Although only certain embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention.
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|US7888267 *||Feb 1, 2008||Feb 15, 2011||Tokyo Electron Limited||Method for etching silicon-containing ARC layer with reduced CD bias|
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|U.S. Classification||438/719, 438/706|
|Cooperative Classification||H01L2924/0002, H01L21/67069, H01L21/32137|
|European Classification||H01L21/67S2D8D, H01L21/3213C4B2|
|Nov 16, 2005||AS||Assignment|
Owner name: TOKYO ELECTRON, LTD., JAPAN
Free format text: ASSIGNMENT OF ASSIGNORS INTEREST;ASSIGNOR:KO, AKITERU;REEL/FRAME:017241/0647
Effective date: 20050929
|Sep 28, 2012||FPAY||Fee payment|
Year of fee payment: 4
|Dec 23, 2016||REMI||Maintenance fee reminder mailed|
|May 12, 2017||LAPS||Lapse for failure to pay maintenance fees|
|Jul 4, 2017||FP||Expired due to failure to pay maintenance fee|
Effective date: 20170512